Ribbed V-belts function, for example, for transmitting force in areas of use which include office machines to the heaviest machine drives. Ribbed V-belts are also used in motor vehicles in different configurations. During use, the ribbed V-Belts are subjected to the most different operating conditions. High requirements are imposed with respect to resistance to wear, noise and dynamic loading. The belts should have the longest possible service life and, at the same time, reduced running noise especially in the area of motor vehicles and household products. Noises arise in frictionally-engaged drive belts such as ribbed V-belts because of friction conditions between drive discs and the belt surface which cause squeaking sounds because of oscillation or vibration.
To reduce the development of noise in frictionally-engaged drive belts and at the same time to improve resistance to wear, United States patent application publication 2003/0139242 A1 discloses a belt which has an outer coating containing polymer on parts of its surface, for example, on the rib surface in ribbed V-belts. This coating is bonded and/or interlaced or cross linked with the rubber or rubber-like plastic of the base body via a vulcanization process. Furthermore, the belt has a flocking material of aramide fibers on its surface of which a portion is bound into this layer only with a partial length. The polymer-containing outer coating is applied as a solution or in liquid form and operates as an adhesive for the fibers during the flocking operation. The coating can be, for example, a rubber solution, a urethane system or a system on the basis of cyanic acrylate in organic solution. The outer coating can additionally contain fluoropolymers. Ribbed V-belts having a coating of this kind are manufactured with the aid of a time-intensive and personnel intensive flocking method. First, the polymer-containing outer layer must be applied to the blank via spraying, coating or dipping. A coating of this kind, as a rule, has a layer thickness of only 50 μm. Thereafter, the flocking takes place with which there is often a high loss of flocking material because of material which does not adhere. Thereafter, and when using coating solutions containing solvents, the blank must be vented in advance of vulcanization over long time spans to remove the solvent because residual amounts of solvent can lead to hollow spaces and inhomogeneities in the product during the vulcanization. However, even after venting and the vulcanization, certain quantities of solvent can remain in the product which evaporate in the course of the product's service life. Also because of this later evaporation of residual solvent, the characteristics of the product can deteriorate. Thus, the volume, for example, of the rubber body decreases after complete evaporation of the solvent and the stability as to form and the physical characteristics can change thereby afterwards which must be considered especially for products subjected to high load. In addition, an odor can occur because of the escaping residual solvent. One considers the above-mentioned aspects in that the rubber product is stored for some time in advance of a test or check and in advance of use. In this way, one must maintain a large inventory which is not wanted for economic reasons. If the flocking fibers are rubbed off in the course of belt use, the layer (approximately 50 μm), which contains the polymer, hardly offers protection against wear.
German Patent 4,318,454 discloses rubber-toothed belts made of elastomeric material which have a high resistance to wear and a long service life and are manufactured with reduced technical complexity. In order to achieve this, the outer surfaces of the teeth have a coating which is made of a fiber-reinforced polymer material, for example, an elastomer having a 10% to 80% fiber concentration per polymer component with the fiber concentration of the elastomer being greater than in the remaining elastomer base body. There is nothing stated in German patent publication 4,318,454 as to the thickness of the coating. A coating of this kind often does not provide the wanted results in ribbed V-belts with respect to noise performance.
U.S. Pat. No. 4,657,526 discloses V-belts having a high transverse stiffness and longitudinal flexibility. The belt body of these V-belts is built up completely of individual elastomeric layers wherein fibers are arranged oriented in one direction in each case. The thickness of each layer is less or equal to the average length of the fibers present in the layer. The fiber concentration in the layers cannot be selected to be very high because the elastic characteristics of the belt body would deteriorate. The resistance to wear and the noise performance of such belts is not adequate for many areas of use.